lens is fine, probably want to check the in-camera settings. I think you could bump up the saturation quite a bit, and maybe adjust the white balance. Get away from Auto WB if you are using it. I don't know if the XTi offers these options, but check. Could save you a lot of post-processing time.

You can do a lot in-camera. I did this 100% in-camera, no post-processing other than cropping: